Electrical utility revenue meters, or simply revenue meters, are typically attached to an electrical system being metered through a meter-mounting device. A commonly available meter-mounting device is a meter base that includes a plurality of current jaws that are electrically connected to the power lines of the facility being metered. The meter includes current blades that are received by the current jaws to provide the electrical connection.
The current jaws also serve to align the meter in proper physical registration with the meter base. Meters have to be carefully aligned with meter bases for several reasons. For example, proper alignment ensures an accurate fit which, in turn, provides a seal to protect the interior of the meter and meter device from the elements and weather. In addition, proper alignment ensures a secure fit of a meter security seal to the meter. A meter security seal is a mechanical device that prevents removal of the meter from the meter base without a special tool. The purpose of the meter security seal is to prevent tampering. Several known types of security seals exist, and all require a relatively accurate fit between the meter and the meter base.
The current jaws assist in aligning the revenue meter with the base by forcing the current blades into a particular position, similar to a plug into a socket. The current jaws, however, only provide alignment along one dimension. Specifically, the jaws contact both sides of the current blades and thus serve to align the meter in a side to side relationship. Absent other alignment features, however, the current blades could typically be disposed at any vertical location within jaws. The term "vertical" as used herein, refers to the vertical direction from the perspective of viewing the revenue meter face.
To align meters in proper vertical registration with a meter base, additional meter blade alignment mechanisms must be used. Such vertical alignment mechanisms include blade guides and flash shields, both of which are well known in the art. Blade guides may either be inner blade guides or outer blade guides.
Blade guides are disposed adjacent to and substantially abutting the meter base jaws. In particular, each blade guide is positioned to engage an edge of a standard current blade when the current blade is inserted into the jaws. Accordingly, the jaws and the blade guides guide the meter into proper registration as the current blades are inserted into the jaws. All of the meter blade alignment mechanisms, including the jaws, are designed to cooperate with ANSI standard electrical utility meter current blades. Current blades have a predefined standard thickness of 0.093 inches and a predefined width of 0.760 inches, and have predefined and standard alignment and positioning.
While meter base jaws contact both sides of the current blades to secure the meter within the meter base, the blade guides typically only contact one of the edges of the current blades. In particular, outer blade guides contact only the outer edge of each of the current blades, and the inner blade guides contact only the inner edge of each of the current blades. The outer blade guides provide an upward guiding force onto the bottom current blades, and a downward guiding force onto the top-most blades. The opposing guiding forces on top and bottom blades force the meter into a substantially precise vertical alignment with the meter base. Similarly, the inner blade guides contact only the inner edge of the current blades, thereby providing a downward guiding force on the bottom blades and an upward guiding force on the top blades to align the meter. Such opposing forces urge the meter into a substantially precise vertical alignment.
The choice of which vertical alignment mechanism is used in a particular base or facility is typically controlled by either the electrical construction contractor or the utility. In any event, the meter manufacturer typically does not control the type of meter base, but must produce a meter that is compatible with meter bases using any of the standard vertical alignment mechanisms. The provision of meters compatible with the various vertical alignment mechanisms has historically not been an issue because all of the meter base vertical alignment mechanisms were designed to be compatible with current blades of standard alignment, thickness and width. As a result, meter manufacturers did not need to be concerned with compatibility with the various vertical alignment mechanisms if they employed standard current blades
One drawback, however, to providing meters having current blades of a standard alignment, thickness and width is that current blades of such standard dimensions significantly affect the material cost of the meter. In particular, current blades are typically constructed of copper, or another conductive metal, and the standard dimensions are relatively large and require a significant amount of metal. As a result, standard current blades represent a substantial portion of the overall meter manufacturing costs.
Moreover, current blades are typically integrally formed with current coils that are located within the meter. To simplify manufacturing costs, the current blades and current coil often have substantially the same thickness and width. As a result, the relatively large dimensions of the standard current blades will dictate relatively large dimensions in the current coil, thereby further increasing costs.
For example, the current coil and current blades are commonly formed by stamping or cutting an elongated straight piece of copper (or other conductive material) having the width and thickness of the current blades. The ends of the elongated piece of copper are then bent to for a "C" shape. The ends of the "C" protrude outward the meter and form the current blades. In such configurations, the large thickness and height requirements of the current blades also defined the current coil thickness and height.
Prior art methods attempted to reduce costs by reducing the width of the current coil. However, to achieve compatibility with meter bases having any of the known vertical alignment mechanisms, the current blades were required to maintain the standard width. Accordingly, several methods of generating current coils were developed in which the body of the current coil had less width than the current blades. One method included attaching two current blades to a pre-formed current coil of lesser width. While such a design can reduce the material costs of the current coil/current blade arrangement, that design undesirably introduces additional manufacturing steps. Moreover, such an arrangement does not decrease the material costs specifically associated with the current blades themselves.
A need, therefore, exists for a meter having a current blade configuration that reduces material costs associated with the current blades and current coils of the meter without increasing the complexity of manufacture of the meter.